Disposable syringe



1954 R. w. OGLE DISPOSABLE SYRINGE Filed July 9, 1951 2 Sheets-Sheet l I I :5 Z .I '7 2 J 1H 3 .Z' 1H Q 2 i t HINVENTO Nov. 9, 1954 R. w. OGLE DISPOSABLE SYRINGE Filed July 9, 1951 IF'J JU Fjg. 171

2 Sheets-Sheet 2 I I a 4 u 1 r I I i I IN V EN TOR.

Irronways DISPOSABLE SYRINGE Robert W. Ogle, Pasadena, Calif, assignorof one-half to Cutter Laboratories, Inc., Berkeley, Calif., a corpora- .tion of California Application July 9, 1951, Serial No. 235,807

11 Claims. (CL 128-218) invention relates to a disposable syringe and more particularly to a disposable syringe adapted to be packed with a dose of medicant sealed and distributed so that the user has simply to inject the packed dose and then dispose of the syringe.

The body of the syringe, including the plunger which also serves as a cork and the barrel itself, is formed of polyethylene plastic. The needles are of conventional cannulae steel and the piston is molded of rubber.

It is therefore one object of this invention to provide a iiikslposable syringe adapted to be prepacked and sea e It is a further object of this invention to provide such a disposable syringe having good qualities for the storing of medicants.

It is a further object of this invention to provide such a disposable syringe inwhich a novel method is employed for fixing the needle to the. barrel.

It is a further object of this invention to provide such a disposable syringe having a rubber piston embodying novel features.

It is a further object of this invention to provide such a disposable syringe which can be assembled and thereafter sterilized prior to shipment.

It is a further object of this invention to provide such a disposable syringe which in its shipping condition has the needle securely sealed against contamination and in which the open end of the needle is provided with a dual seal.

It is a further object of this invention to provide such,

a disposable syringe in which provision is, made forthe utilization of a separate and removable needle.

, These and other advantages of the invention will be apparent from the annexed specification in -which:

.Figure l is a plan view of a syringe embodying the present invention in its sterilizing position.

Figure 2 is an end view taken on the 1ine s 2 2 of Figure 1. v

Figure 3 is a plan view of the device shown in Figure 1, shown in its completely sealed or shippingposition.

Figure 4 is a section taken on the line 44 of Figure 3 Figure 5 is a section similar to Figure 4 with the syringe prepared for injection of the medicant.

Figure 6 is an enlarged fragmentary section of the upper end of the barrel.

Figure 7 is a section taken along the line 7-7 of Figure 6.

Figure 8 is a section similar to that shown in Figure 6 showing an alternative construction.

Figure 9 is an enlarged plan view of the rubber piston.

Figure 10 .is an enlarged fragmentary section of the upper end of the plug.

'Figure 11 is a section similar to Figure 10 showing the sealing of the needle.

Figure 12 is a section similar to Figures 10 and-11 sho g he a ion it h ne dle Pul e ut-o the p Figure 13 is an idealizeddrawing for thepurpose of illustrating the formation of the plug in thQ interior of the needle. 7 v

Figure 14 is a plan view. partly in section and Partly inphantom of analternative embodiment of the present invention.

1 Figure 15 .is an enlargd, fragmentary section of the 2,693,803 Patented Nov. 9, 1954 Figure 16 is an enlarged fragmentary plan view of the the removable needle in place.

Figure 17 is a fragmentary section showing the method of inserting the needle in the barrel.

Referring now more particularly to Figure 1, the syringe includes a barrel indicated .generally by the numeral 20, which barrel is provided at its upper end with a flange 21, preferably rectangular in shape as shown in Figure 2, to prevent rolling 'of the syringe. The entire barrel 20 is formed of polyethylene plastic and the walls have a thickness in the order of 60/1000 inches, which thickness of polyethylene plastic has been discovered to give a good vapor moisture transmission characteristic thus enabling storing of medicants over long periods of time without undue loss.

The upper end of the barrel 20 is provided with an extension 22 in the form of a centrally disposed post or boss. This post is notched as at 23 throughout a portion only of its length. As shown in Figure 7, there may be three of such notches 23. The interior of the barrel 20 is hollow and at the upper end the walls thereof taper as at 24 converging towards the needle 25. The needle 25 is driven, as hereafter explained, centrally throughout post 22 and as shown in Figures l-6 has its inner end aligned with the edges of the tapered walls 24. However, an alternative structure is shown inFigure 8 wherein the needle 25 is not driven completely through the end of the barrel 20 and terminates short thereof as shown at 26. In this embodiment'a bore 27 communicates the interior of the hollow needdle 25 with the interior of the barrel 20 and a shoulder 28 is formed adjacent the bore.

The needle 25 is provided with a tapered open end 29. A cork 30 is provided, which cork 30 is hollow and is provided with a flange 31 at one end and a male thread member 32 at the other end thereof. The cork 30 is hollow and at its upper end, the walls are provided with a converging taper 33. The upper end of the cork 30 is also provided with a thickened solid portion 34. The cork 30 is manufactured from polyethylene plastic and its walls, except in the thickened portions, are of the order of V inch thick. The interior or bore of the cork 39 is preferably of a smaller diameter than the exterior of the post 22 thus providing a press fit between the post and. the interior of the cork which requires a slightexpansion of the walls of the cork when the plug is inserted and thus insures a good seal.

The barrel 20 is adapted to receive a rubber piston 35. This rubber piston is provided with a female thread 36 and a pair of ridges 37 and 38. The female thread 36 extends into the rubber plunger 35 at least beyond the first ridge 38. As shown in Figure 5, the cork 30, when it is desired to use the syringe, is removed from the post 22. and the male end thereof is threaded into the female thread 36 in the rubber plunger. The last one or two threads on the end of the male member 32 pass beyond he dge 8 s c ea ly h n i F e 5 The male thread 32 is preferably made $5 or @io inch larger in diameter than the interior diameter of the female thread 36 so that upon threading of the male member 32 into the piston 35, the piston'35, will be expanded laterally. This condition is shown in Figures 4 and 5.

The disposable syringe may be .prepared for shipping to a customer priorto filling with medicant as follows:

Referring now to. Figure .l, we note that the cork 30 is not completely seated upon the post 22. In this condition the upper end of the needle 25 is also free of the upper end 34 of the cork. sterilizing gas can thus be circulated through the syringe through the open end of the barrel 20, the piston 35 being removed, and the grooves 23 to. completely sterilize the interior of the .cork, the exterior and interior of the needle and the interior of the barrel 20. The sterilizing gas can then be withdrawn by vacuum. After this is done, the cork 30 is pushed further on to the post 22 to the position shown ,in Figure 4, fin which case the syringe issealed, It willbe apparent that there is provided by the cork 30 three seals, one seal occurring by reason of'the coaction of the post22 with the interior'of the cork and the expandingjof the cork pensated for by the exposed to moisture in the region of the post. The second seal occurs between the outside of the upper end of the needle and the material of the thickened end 34. The third seal is provided to the interior of the upper end of the needle by reason of the plug 40.

Referring now to Figures 10, ll, 12 and 13, the formation of the seal at the upper end of the needle will be more fully described. The tapered walls 33 serve as a guide to center the needle as near as possible in the center of the thicknened portion 34 to prevent the needle from moving sideways and perhaps emerging from the cork.

When the needle is driven into the thickened portion 34 of the cork the needle cuts a plug as shown in Figures 11, 12 and 13, which plug 40 is not severed at any time from the remaining portion of the material of the thickened end 34. As shown in Figure 12, when the needle is removed from the cork, the plug 40 remains and is pulled outof the end of the needle.

Figure 13 is shown in order to more completely describe this action. Figure 13 illustrates the condition of the needle and cork if one were to take and pull the material away from the sides of the needle. As shown at 41 and 42, the plug 40 would remain within the end of the needle as shown but not severed from the remaining material of the thickened end 34.

As long as the needle does not go completely through the polyethylene plastic, no plug will ever be severed from the polyethylene; This discovery has made possible the use of polyethylene in the cork member for the following reasons:

First, polyethylene is a waxy semi-crystalline substance which permits cutting by any sharp instrument with comparative ease. Secondly, the rigidity of polyethylene in the thick section is such that the plug cut by the insertion of the needle is substantially of the same diamter as the inside diameter of the needle and is certainly not larger than the interior of the needle as might be the case with a material having a much higher elastic deformation, such as, for example, soft rubber. Thirdly, the tensile strength of polyethylene is such that the core produced by the insertion of the needle is sufficiently well attached to resist tearing away from the parent material when the needle is withdrawn. Lastly, polyethylene, because of its waxy nature,'has a very favorable coeificient of friction and does not tend to cling to the side wall of the material when the needle is removed from the plug.

It will be obvious from the foregoing that when the needle 25 is driven into the thickened member 34 as shown in Figure 13, there is thus afiorded a double seal, the first of which is formed on the exterior of the walls of the needle by the material of the thickened member 34, and the second of which is formed on the interior walls of the needle by the core 40. This double seal is of vital importance in assuring shelf life to medicants stored in syringes of this type. Due to the fact that polyethylene plastic is capable of taking a small degree of permanent set, the seal upon the outside of the needle can possibly be broken. This, however, will be comfact that the core on the inside is from the stored medicant and will therefore slightly swell thus assuring that the seal upon the inside of the needle is not broken.

' I have mentioned above that the male member 32 is inserted in the female member 36 to the extent that one or two of the threads thereof pass beyond the ridge 38. Thus the piston 35 in the ridge 38 when being driven into thebarrel is being pulled rather than pushed, and the ridge 37 is being pushed rather than pulled and the reverse action takes place upon the withdrawal of the piston from the barrel. This permits a sure and firm grip of the ridge 37 and 38 upon :the inner-walls of the barrel; Furthermore, the piston is designed so that the needle 25 as shown at 50. This needle is driven through the center of the post 22 until it emerges in the interior of the barrel 20. The mandrel 50 thus makes a small hole in the plastic material by merely spreading the material without cutting a core. The needle 25 has its lower edges bevelled as shown at 51 and the needle follows a short space behind the mandrel 50. In this manner the needle is driven into the bore made by the mandrel 50 without cutting away any material and hence the needle is imbedded in the plastic material under hoop tension. As shown in Figure 8, the end of the needle may in fact terminate short of the interior of the barrel 20 and hence rest upon the shoulder 28 to give further support to the needle. However, this is not found to be essential.

The above described method of inserting the needle in the plastic is the only method found practical. It has been discovered that when a straight needle such as that employed in the present invention is molded in the polyethylene, the polyethylene will separate from the needle and fail to hold the needle satisfactorily.

Referring now to Figures 1416, there is shown an alternative embodiment in which the needle 25 is .not used. The cork 30 may in all respects be similar to the cork 30 of the previous embodiment although it is apparent that a much shorter and smaller cork may be used. The barrel 60 is essentially similar to the barrel shown in the previous embodiment and the piston 35 may be identical.

The difference in this embodiment lies in the fact that the post 22 at the upper end of the barrel is provided with an interior bore 61 and a short extension 62. The bore 61 extends only partially into the extension 62. Thus the extension 62 forms an enclosure for the bore 61. The physician desiring to use this embodiment of the invention will cut a portion of the extension '62 from the post 66 as shown in Figure 15 and will then insert upon the post 66 a conventional needle having an enlarged hub 63 with a tapered wall 64 adapted to fit the tapered end 65 of the post 66. Such a needle is shown in Letters Patent of the United States No. 2,076,121. This condition is shown in Figure 16.

In each embodiment of this invention the walls of the barrel 20 have sufficient resiliency so that an operator can actually grip the piston 35 by depressing the walls of the barrel and hold the piston during the threading in or threading out of the male member 32 into the female member 36.

As explained above, the male members 32 are preferably formed with a diameter or A inch in excess of the interior diameter of the female threads 36 to cause the expansion of the piston 35 as the threads are made up to insure that the piston has a'leak-proof contact within the walls of the barrel. This is important in case the piston 35 has taken a permanent set.

While there has been described what is considered a preferred embodiment of the present invention, it will be appreciated by those skilled in the art that various changes and modifications can be made therein without departing from'the essence of the invention and it is intended to cover herein all such changes and modifications as come'within' the true spirit and scope of the appended claims.

What is claimed is:

1. A syringe comprising: a hollow tubular member having an open end and a closed end; a boss formed on said closed end and extending outwardly in' axial alignment with said tubular member; a hollow needle imbedded in said boss and said closed end, communicating outer diameter of the ridges 37 and 38 are greater than a the interior diameter of the barrel 20. We have found in practice thatthe-ridge 37 should be in the order of inch greater in diameter and the ridge 38 in the order of inch greater in diameter than the interior diameter of the barrel. By reason of this construction of the piston '35, the syringe is designed to be aspirated.

Referring'now more particularly to Figure 17, there is shown the method of imbedding the needle 25 in the polyethylene plastic. A solid sharpened mandrel having an exterior diameter'ot or inch less than the interior diameter of the needle 25 is provided situated within the with said hollow tubular member and extending outwardly from saidboss; a second hollow'tubular member having an open end and a closed end, said open end being adapted to seat upon said boss with a press -fit and seal with'said boss; said hollow tubular members being formed .of polyethylene plastic material; saidsecond hollow tubularmernher being adapted to surround'saidhollow needle and being proportioned with respect thereto so that when it is fully seated upon said boss the open endof said needle is fully imbedded in the closedend of said second hollow member; said second hollow tubular member at its closed end having inwardly tapered side walls adapted to direct the point of said'needle to be imbedded in the center of said closed end; Sflld open end of said needle. being adapted to cut a plug of material of said closed end when imbedded therein, but to releasesaid plug when removed from said closed end; a member formed on the exterior of 'said closed end of said second hollow-member having a male thready'apiston adapted 'to be :received insaid first hollow tubular member; said piston havinga female thread adapted'to receive said'malethread of said second tubular member to form aplunger; =said pistonbein'g formed of a rubber-like materialand havinga-plurality of spaced annular fianges'upon the exterior'thereof-having an outer diameter exceeding theinner diameter of said first tubular member; 'saidfemale thread having adepth so that when fully tightened therein at =-least--one flight of said male thread extends into said piston beyond one of said annular flanges.

2. A" syringe comprising: a hollow tubular member having an openendand a 'closed end; -a boss formed on said closed end and extending outwardly in axial alignment with said tubular member;ahollow'needle imbeddedin said-boss and'said closed end, communicating with said hollow tubular-member and extending outwardly from-said boss;:a secondhollow' tubular member having an open endand'a closedend, said open"end'being adapted to seat uponsaid boss with a press fit and seal with said boss; said hollow tubular members being formed of polyethylene plastic material; said second hollow tubular member being adapted to surround said hollow needle and being proportioned with respect thereto so that when it is fullyseated upon said boss the open end ofsaid needle is fully imbedded in the closed end of said second hollow member; said second hollow tubular member at its closed end having inwardly tapered side walls adapted to direct the point of said needle to beimbedded in the center of saidclosed-endjsaid open end of said needle being adapted to cut a plug of material of said closedend when imbedded therein, but to release said plug when removed from said closed end; a member formed on the exterior of said closed end of said second 'hollow member having a male thread; a piston adapted to be received in said first hollow tubular member; said piston having a female thread adapted to receive-said male-threadof said second tubular member to form aplungerrsaid piston being formed of a rubber-like material and having a plurality of spaced annular flanges upon the exterior thereof having an outer diameter exceeding the inner diameter of said first tubular memberjsaid female thread'having a depth so that when fully tightened therein at least one flight of said male threadextends into 'said piston beyond one of said annular flanges; one of 'said-annularflanges toward the open end of said first tubular member having an outer diameter greater than the other ofsaid annular flanges.

3. A syringe comprising: a hollow tubular member having an open end and a closed end; a boss formed on said closed end and extending outwardly in axial:'alignment with said tubularmemben'a hollow needle imbedded in said boss and said-closed end, communicating with said hollow tubular member and-extending" outwardly 'from said boss; a second hollow tubular 'member having an open end and a closed-end;said'open end being adapted to seat upon said-boss with apre'ss fit and seal-with said boss; said hollow tubular members being formed of polyethylene plastic material'ysaid second hollow 'tubular member being-adapted to surround said hollow needle and being proportioned with respect thereto so that .when

it is-fully seated upon said boss the open end of said needle is fully imbedded in the closed=end of said'second hollow member; said second hollowtubular member at its closed end having inwardly tapered side walls adapted to direct the point of said needle to be imbedded in the center of said closed end; said open end of said needle being adapted to cut a plug of material of said closed end when imbedded therein, but to release said plug when removed from said closed end; a member formed on the exterior of said closed end of said second hollow member having a male thread; a piston adapted to be received in said first hollow tubular member; said piston having a female thread adapted to receive said male thread of said second tubular member to form a plunger; said boss having a longitudinally extending groove extending from its free end a portion only of its length.

4. A syringe comprising: a hollow tubular member having an open end and a closed end; a boss formed on said closed end and extending outwardly in axial alignment with said tubular member; a hollow needle imbedded in said boss and said closed end, communicating with said hollow tubular member and extending outwardly from said boss; a second hollow tubular member hav- 6 ing an openend anda elosed' end; said open end being adapted to 'seat upom'said .bo'ss with 'a pre'ss fit-"and seal with "said boss; said hollow tubularmembersbeingformed of polyethylene plastic material; =said second hollow tubularmember=being adapted to surround said hollow needle and "being' proportioned iwith respect-thereto 1 so that when it is 'fully -seated upon saidboss the openend of -said needle is fully imbedded in the closed end of said second hollowmember; said second hollow tubular member at its closed'end having-inwardly tapered side walls adapted to-direct the point of 'saidneedle-to be imbeddedin the center ofsaid closed'end; said open end of said-needle being adapted to cut, a plug of material of said closed endwhenimbedded therein, but to release said plug when removed'from said closed end; a member formed on the exterior ofsa'id closedend of'said second hollow'me'mberhaving 'a-male thread; a piston'adapted to-be received in-'saidfirst 'hollow tilbularmember; said piston having a'femalethread' adapted to receive said male thread of said second tubular member to form a plunger; said boss having an axial bore; said needle being disposed in said bore and having an outer 'diameter greater than the initial innerdiameterof said-axial bore'whereby said needle is held under tension in said bore.

5. A" syringe comprising: a hollow tubular member having an' open end "and a closed end; a boss formed on saidclosed end andextending outwardly in axial alignment"withisaid tubular member; a hollow needle imbedded in said boss and said closed end, communicating with saidho'llow tubular'member and extending outwardly from saidboss; a second hollow. tubular member having an'op'enendand a closed end, said open end being adapted tor-seat npon'said boss 'with a press fit and seal with said boss; said hollow tubular members beingformed of polyethylene plastic material; said second hollow tubular'ni'ernberbeing adapted to 'surround' said hollowneedle and being proportioned withrespe'ct thereto so that when it i'stully 'seated'uponsaid bossthe open end of said needle isfully imbedded in the closed end of'said'second hollow member; said second hollow-tubular member at its closedend having inwardly tapered-slde walls adapted to-dire'ct the point of said needle to belim'bedded'in the.

center .ofnsaidclosed end; said open'end of said needle being-adapted .tocut; a plug of material of said closed endtwhen imbedded therein, but to release said plug when removed lfromtsaid closed end; a'member formed on the exterior.ofsaid-closedend ofsaid second hollow member having a male thread; a piston-adapted to be. received in said firstvhollo'w tubular member; said piston having a female thread adapted to receive said male thread of said'seeond tubular member to form aplunger;= sa d boss having an axial boreg-tsaidneedle beingdisposed nsaid bore-and"having an outer diameter greater than the m1- tial-inner diameter ofisaidaxial bore whereby said needle is-held under tensionin said bore; said needle extending a portion only of said bore. 7

- 6. Ai-syringeiicomprising: a hollow tubular :member having aniopen end-sand a'closed end; a boss formed on said closed: end and extending outwardly in axial alignment with said tubular/member; said boss having a frustoconical: portion; aiborerintsaid-boss communicating with hollow tubular-member; an extension on said boss forming a' closure for said bore; said extension beingadapted to be severed ifrom saidaboss'to open communication to said hollow: tubular.xmember; a second. hollow tubular member having an open end and a closed end, said open end being adapted to seat upon said boss with a press fit and seal with said boss; said hollow tubular members being formed entirely of polyethylene plastic material; a member formed on the exterior of said closed end of said second hollow member having a male thread; a piston adapted to be received in said first hollow tubular member; said piston having a female thread adapted to receive said male thread of said second tubular member to form a plunger; said frusto-conical portion being adapted to receive and support a tapered section of an enlarged hub of a hollow needle.

7. A syringe comprising: a hollow tubular member having an open end and a closed end; a boss formed on said closed end and extending outwardly in axial alignment with said tubular member; said boss having a frustoconical portion; a bore in said boss communicating with hollow tubular member; an extension on said boss forming a closure for said bore; said extension being adapted to be severed from said boss to open communication to said hollow tubular member; a second hollow tubular member having an open end and a closed end, said open end being adapted to seat upon said boss With a press fit and seal with said boss; said hollow tubular members being formed entirely of polyethylene plastic material; a member formed on the exterior of said closed end of said second hollow member having a male thread; a piston adapted to be received in said first hollow tubular member; said piston having a female thread adapted to receive said male thread of said second tubular member to form a plunger; said frusto-conical portion being adapted to receive and support a tapered section of an enlarged hub of a hollow needle; said piston being formed of a rubber-like material and having a plurality of spaced annular flanges upon the exterior thereof having an outer diameter exceeding the inner diameter of said first tubular member; said female thread having a depth so that when fully tightened therein at least one flight of said male thread extends into said piston beyond one of said annular flanges.

8. A syringe as set forth in claim 6 in which said tubularhmembers have walls of a thickness of at least 1nc 9. A syringe comprising: a hollow tubular member having an open end and a closed end; a boss formed on said closed end and extending outwardly in axial alignment with said tubular member; said boss having a frustoconical portion; a bore in said boss communicating with hollow tubular member; an extension on said boss forming a closure for said bore; said extension being adapted to be severed from said boss to open communication to said hollow tubular member; a second hollow tubular member having an open end and a closed end, said open end being adapted to seat upon said boss with a press fit and seal with said boss; said hollow tubular members being formed entirely of polyethylene plastic material; a member formed on the exterior of said closed end of said second hollow member having a male thread; a piston adapted to be received in said first hollow tubular member; said piston having a female thread adapted to receive said male thread of said second tubular member to form a plunger; said frusto-conical portion being adapted to receive and support a tapered section of an enlarged hub of a hollow needle; said piston being formed of a rubber-like material and having a plurality of spaced annular flanges upon the exterior thereof having an outer diameter exceeding the inner diameter of said first tubular member; said female thread having a depth so that when fully tightened therein at least one flight of said male thread extends into said piston beyond one of said annular flanges; one of said annular flanges toward the open end of said first tubular member having an outer diameter greater than the other of said annular flanges.

10. A syringe comprising: a hollow tubular member having an open end and a closed end; a boss formed on said closed end and extending outwardly in axial alignment with said tubular member; a second hollow tubular member having an open end and a closed end, said open end being adapted to seat upon said boss with a press fit and seal with said boss; said hollow tubular members being formed of polyethylene plastic material; a member formed on the exterior of said closed end of said second hollow member having a male-thread; a piston adapted to be received in said first hollow tubular member; said piston having a female thread adapted to receive said male thread of said second tubular member to form a plunger; said piston being formed of a rubber-like material and having a plurality of spaced annular flanges upon the exterior thereof having an outer diameter exceeding the inner diameter of said first tubular member; said female thread having a depth so that when fully tightened therein at least one flight of said male thread extends into said piston beyond one of said annular flanges; said male thread having a diameter slightly larger than the interior diameter of said female thread.

11. A syringe comprising: a hollow tubular member having an open end and a closed end; a boss formed on said closed end and extending outwardly in axial alignment with said tubular member; a hollow needle imbedded in said boss and said closed end, communicating with said hollow tubular member and extending outwardly from said boss; a second hollow tubular member having an open end and a closed end, said open end being adapted to seat upon said boss with a press fit and seal with said boss; said hollow tubular members being formed of polyethylene plastic material; said second hollow tubular member being adapted to surround said hollow needle and being proportioned with respect thereto so that when it is fully seated upon said boss the open end of said needle is fully imbedded in the closed end of said second hollow member; said second hollow tubular member at its closed end having inwardly tapered side walls adapted to direct the point of said needle to be imbedded in the center of said closed end; said open end of said needle being adapted to cut a plug of material of said closed end when imbedded therein, but to release said plug when removed from said closed end; a member formed on the exterior of said closed end of said second hollow member having a male thread; a piston adapted to be received in said first hollow tubular member; said piston having a female thread adapted to receive said male thread of said second tubular member to form a plunger; said piston being formed of a rubber-like material and having a plurality of spaced annular flanges upon the exterior thereof having an outer diameter exceeding the inner diameter of said first tubular member; said female thread having a depth so that when fully tightened therein at least one flight of said male thread extends into said piston beyond one of said annular flanges; said male thread having a diameter slightly larger than the interior diameter of said female thread.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 600,803 Robinson et al Mar. 15, 1898 938,951 Bell Nov. 2, 1909 1,144,343 Benmosche et al June 29, 1915 2,068,927 Nevin Ian, 26, 1937 2,490,553 Smith Dec. 6, 1949 2,497,562 Smith Feb. 14, 1950 2,550,394 Young et al Apr. 24, 1951 2,551,414 Burnside May 1, 1951 2,578,394 Blackman Dec. 11, 1951 FOREIGN PATENTS Number Country Date 90,189 Switzerland Aug. 1, 1921 573,611 Great Britain Nov. 28, 1945 

